1. Field of the Invention
The present invention relates to an ink jet recording apparatus, especially the one capable of recording images having a tone, and more specifically to an ink jet recording apparatus that can record images with a plurality of inks with different densities for each color.
This invention can be applied to all kinds of recording apparatuses that record on recordable media such as paper, cloth and OHP transparencies and also to printers, copying machines and facsimiles.
2. Description of the Prior Art
The ink jet recording apparatuses are being used on printers, copying machines and facsimiles because of their advantages including low noise, low running cost, ease of reducing the size of apparatus, and ease of introducing color printing.
Color recording by the ink jet recording apparatus generally uses three color inks, cyan (C), magenta (M) and yellow (Y), or four including an additional black (Bk) ink. Using these inks, red (R) for instance is produced by M+Y, green (G) by C+Y, and blue (B) by M+C.
For improved halftone recording, a plurality of inks with different densities are used for each color, with an appropriate ink with an optimum density selected for printing.
Arranging the ink tanks containing a plurality of color inks with different densities near recording heads in the recording apparatus and moving the ink tanks along with the recording heads has the following drawbacks:
1. It is necessary to increase the capacity of a motor as a means for moving them, resulting in an increase in the size of the recording apparatus and cost.
2. The fact that many kinds of inks are used means degraded ease of use since replacement and supplement for each color ink is required when refilling the empty tanks and increases the kind of ink merchandised to increase burden in the merchandise distribution channels from manufacturers to users.
Another type of the ink jet recording apparatus is available, in which sub-ink tanks, mounted on recording heads so that they move together, are made small in volume and are supplied required amounts of inks from separate main tanks of large volume.
This type of apparatus, though it eliminates the first problem, cannot overcome the second one. Especially when a particular main tank becomes empty, it must be replaced by user and, depending on the kind of images being recorded, may require frequent replacement.